Sodium Chloride (NaCl) is used for windows, lenses and prisms where transmission in the 0.25 - 16 µm range is desired. Because of its low absorption, Sodium Chloride is being used in high power laser systems. Polished surfaces must be protected from moisture by exposing to only dry atmosphere or by using a heating element to maintain the Sodium Chloride above the ambient temperature. Sodium Chloride can be used up to 400°C. The material is sensitive to thermal shock. Irradiation generates color centers.
      Potassium Chloride (KCl) is used for infrared windows, lenses and prisms when transmission in the 0.3 - 20 µm range is desired (transmission extends beyond that of Sodium Chloride). Potassium Chloride is soluble in water and polished surfaces must be protected from moisture. Maximum use temperature is 400°C.Potassium Chloride is mainly used for CO2 laser protection windows as an inexpensive disposable material with a low refractive index.
      Potassium Bromide (KBr) is used as IR spectroscopic components, beamsplitters, for CO2 -lasers. KBr is water soluble and must be protected against moisture degradation of polished surfaces. The material cleaves readily, and can be used at temperature up to 300 °C. Irradiation of KBr produces color centers.
      Potassium Iodide (KI)
Potassium Iodide has few specific applications but has some uses in the very deep Infra Red.
      Cesium Iodide (CsI) is useful for infrared having transmission through the visible out to 70 µm in a 2 mm thickness. It is principally used for infrared prisms, cell w indows and as a beamsplitter or as interferometer plates. Cesium Iodide is also furnished as Thallium activated Cesium Iodide for scintillation crystals. Being relatively soft, this material has found application in satellite-borne radiation detectors, which must withstand extreme shock and vibration along with rapid temperature changes. Cesium Iodide precipitated powders are used in solid phase pelleting of samples for infrared spectroscopy. Cesium Iodide is highly water soluble and polished faces of this material may be damaged by moisture in the atmosphere when relative humidity is higher than 35%. CsI can be cut with a band saw. Standard polishing techniques can be used.

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